Background CSF1R-related leukoencephalopathy, also known as hereditary diffuse leukoencephalopathy with spheroids (HDLS), is a rare white-matter encephalopathy characterized by motor and neuropsychiatric symptoms due to colony-stimulating factor 1 receptor (CSF1R) gene mutation. Few of CSF1R mutations have been functionally testified and the pathogenesis remains unknown. Methods In order to investigate clinical and pathological characteristics of patients with CSF1R-related leukoencephalopathy and explore the potential impact of CSF1R mutations, we analyzed clinical manifestations of 15 patients from 10 unrelated families and performed brain biopsy in 2 cases. Next generation sequencing was conducted for 10 probands to confirm the diagnosis. Sanger sequencing, segregation analysis and phenotypic reevaluation were utilized to substantiate findings. Functional examination of identified mutations was further explored. Results Clinical and neuroimaging characteristics were summarized. The average age at onset was 35.9 ± 6.4 years (range 24-46 years old). Younger age of onset was observed in female than male (34.2 vs. 39.2 years). The most common initial symptoms were speech dysfunction, cognitive decline and parkinsonian symptoms. One patient also had marked peripheral neuropathy. Brain biopsy of two cases showed typical pathological changes, including myelin loss, axonal spheroids, phosphorylated neurofilament and activated macrophages. Electron microscopy disclosed increased mitochondrial vacuolation and disorganized neurofilaments in ballooned axons. A total of 7 pathogenic variants (4 novel, 3 documented) were identified with autophosphorylation deficiency, among which c.2342C > T remained partial function of autophosphorylation. Western blotting disclosed the significantly lower level of c.2026C > T (p.R676*) than wild type. The level of microtubule associated protein 1 light chain 3-II (LC3-II), a classical marker of autophagy, was significantly lower in mutants expressed cells than wild type group by western blotting and immunofluorescence staining. Conclusions Our findings support the loss-of-function and haploinsufficiency hypothesis in pathogenesis. Autophagy abnormality may play a role in the disease. Repairing or promoting the phosphorylation level of mutant CSF1R may shed light on therapeutic targets in the future. However, whether peripheral polyneuropathy potentially belongs to CSF1R-related spectrum deserves further study with longer follow-up and more patients enrolled. Trial registration ChiCTR, ChiCTR1800015295. Registered 21 March 2018.

中文翻译：

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CSF1R相关白质脑病的临床病理学特征和异常自噬。

背景 CSF1R 相关性脑白质病，也称为遗传性弥漫性球状白质脑病 (HDLS)，是一种罕见的白质脑病，其特征是由于集落刺激因子 1 受体 (CSF1R) 基因突变引起的运动和神经精神症状。很少有 CSF1R 突变在功能上得到证实，发病机制仍然未知。方法为了解CSF1R相关性白质脑病患者的临床和病理特征，探讨CSF1R突变的潜在影响，我们分析了来自10个无关家庭的15例患者的临床表现，并对2例进行了脑活检。对 10 名先证者进行了二代测序以确认诊断。Sanger测序、分离分析和表型重新评估被用来证实研究结果。进一步探索了已识别突变的功能检查。结果总结了临床和神经影像学特征。平均发病年龄为 35.9 ± 6.4 岁（范围 24-46 岁）。女性发病年龄低于男性（34.2 岁对 39.2 岁）。最常见的初始症状是语言功能障碍、认​​知能力下降和帕金森症状。一名患者也有明显的周围神经病变。2例脑活检显示典型的病理改变，包括髓鞘丢失、轴突球体、磷酸化神经丝和活化的巨噬细胞。电子显微镜显示气球状轴突中线粒体空泡化增加和神经丝紊乱。共有 7 个致病变异（4 个新的，3 个记录在案）被鉴定为自身磷酸化缺陷，其中 c.2342C > T 保持自磷酸化的部分功能。蛋白质印迹显示 c.2026C > T (p.R676*) 的水平显着低于野生型。通过蛋白质印迹和免疫荧光染色，自噬的经典标志物微管相关蛋白 1 轻链 3-II (LC3-II) 的水平在突变体表达的细胞中显着低于野生型组。结论 我们的研究结果支持发病机制中的功能丧失和单倍体不足假说。自噬异常可能在该疾病中起作用。修复或促进突变CSF1R的磷酸化水平可能会在未来揭示治疗靶点。然而，外周多发性神经病是否可能属于 CSF1R 相关谱系值得进一步研究，需要更长的随访时间和更多的患者入组。试用注册 ChiCTR, ChiCTR1800015295。2018 年 3 月 21 日注册。